1. Field of the Invention
The invention falls into chemistry elemental organic compounds, more particularly, to new chemical compounds of the known class—mixed ligand complexes of rare earth elements (REE), namely, to compounds di-(nitrate)acetylacetonatobis (1,10-phenanthroline) lanthanide (III) where lanthanide represents TbxEr1-x, applicable for use as a luminescent additive in ink for hidden marking the valuables, which ink can be applied in verification of authenticity of documents, excise tags, banknotes and other securities and products.
2. Description of the Related Art
Among the known REE complexes one can find a heat sensitive luminophor energized by UV-radiation at λenerg equal to 335 nanometers, which luminophor is an element consisting of the europium salts and the cinnamic acid (JP patent application No 57-83580, published 25 May 1982).
Also known is a luminescent composition comprising a REE crystal salt and the organic carboxylic acid, featuring bright luminescence at excitation by an electron beam, X rays or UV-radiation. The REE is, commonly, represented by Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Tm or Yb, wherein an organic carboxylic acid is represented by the benzoic, o-toluil or n-phthalic acid (JP patent application No 57-18779, published 30 Jan. 1982).
However the said compounds are not capable of accumulating the energy of an ionizing radiation and therefore cannot be used as the thermo-luminophors registering radiation previous impact.
Class of mixed ligand complexes of rare earths elements comprises pentanitrate REE 1,10-phenantrolone, where REE-Tb or Dy, or Ho (Shchelokov P. H., Bolotova G. T, Perov V. I, Evstafieva O. N, Nitrate complexes of rare earths with 1,10-phenantrolone in outer sphere, G. inorganic chemistry, 1988, v. 33, No 4, p. 867).
The said complexes of REE are structural analogues of the claimed compounds, however they have very weak luminescence, cannot either accumulate energy or be used as a thermo-luminophor for registration of UV-radiation and X-rays.
The state-of-the-art, by application mode, includes the technical solutions presented in the following sources. Composition for the hidden data recording, comprising solution A containing a luminophor, a binding substance and an organic solvent, and, in addition, solution B, also the containing a different luminophor, a binding substance and an organic solvent, is known, wherein the A/B ratio is within the range of 1:10 to 10:1. For producing a hidden data recording the solution A is placed on a substrate, kept on till evaporation of the solvent followed by generation of a film, then the substrate is processed by the solution B, dried and illuminated by UV-light (see RU No 2057782, published 10 Apr. 1996). The luminophors in this case are represented by the organic compounds creating molecular solutions in organic solvents. The identification data embedded on the substrate in such a manner are visualized at illumination of the surface by UV-radiation, for example, by a mercury lamp.
Also known is the use of colorless ink composed of a solution of an organic luminophor for marking a document with machine-readable tags indiscernible in the visible light. The colorless inks are capable of being visualized on a paper at its illumination by an ultraviolet light (patent application RU No 98101973, published 10 Jan. 2000).
Use of organic luminophors as ink for marking enables producing a bright and high-contrast image at visualization of the recorded identification data, however, the common drawback of such technical solutions consists in the presence of a wide spectrum of fluorescence, intrinsic to all organic luminophors, which feature complicates verification of documents. Besides, the organic compounds do not luminance under X-rays (there is no bright emission), which feature limits the protection degree in case of use of organic luminophors for marking.
This is why the most commonly used luminophors are those which are capable of emitting radiation only in a very narrow range of the wave-length, for example, the compounds of rare earths. The advantage of such luminophors, by comparison with the luminophor emitting the radiation in a wide range of wave-length, consists in that their radiation has more particular spectrum in comparison with the spectrums of radiation of other substances, therefore such luminophors should be recognized as more reliable at automatic control of authenticity of documents (W0 00/39397, published 6 Jul. 2000; patent RU No 2249504, published 10 Apr. 2005).
In the RU patent No 224 9504 the combination of substances with two automatically controllable features for protection of important documents against forgery is proposed. An important document is characterized by the presence of, at least, two luminophors which luminescent features can be automatically controlled independently of each other. The first luminophor irreversibly loses its luminescent capability at the first temperature. The second luminophor irreversibly loses the luminescent capability at the second temperature. The first and/or the second temperature exceed the temperature of inflammation of the important document. It allows univocal identifying the important document both by its appearance and by its ashes and excludes the possibility of illegal regeneration of the materials used for protection against forgery for the producing duplicates of the securities.
In particular cases of embodiment of the invention under the RU patent No 2249504, the first luminophor is, preferably, represented by an inorganic luminophor, the second luminophor is an organic luminophor, and, in a preferable embodiment, such luminophor is represented by the dark blue methylene.
In another alternative the first and second luminophors are the inorganic luminophors containing crystal substances, of which the lattice of the matrix comprises alloying admixtures REE. Preferably, a rare-earth element is chosen from the group comprising neodymium, ytterbium, praseodymium, erbium and holmium. In the preferable embodiment the second luminophor is ZnS:CuCl, and the first luminophor is Y3Al5012:Tb.
The drawback of the said combination of substances consists in low intensity of the luminescence and presence only two levels of protection.
Also known is a fluorescent aqueous stamp mastic containing a water-soluble fluorescent coloring agent emitting light at the wave lengths within the range of 200 to 700 nanometers due to action of radiation with the wave lengths within the range of 200 to 700 nanometers, a water-soluble not fluorescent coloring agent, a binding agent represented by polyethylene glycol with molecular weight of 200 to 60000, the low molecular alcohols and water and, in addition, a water-soluble organic luminophor with the radiation range of 450 to 500 nanometers and with a wide range of excitation of some 200 to 400 nanometers, and also in the capacity of europium β-diketonat-europium tris-tenoiltriftoratsetononat (RU patent No 2220997, published 10 Jan. 2004).
The main drawbacks of the stamp mastic for hidden data recording consist in that they multi-component and provide for one protection level only, which makes this mastic inapplicable for reliable protection of products against forgery. Photo stability of europium used in the mastic is moderate, its spectrum is generally known for a long time.
The luminescent composition for marking securities, based on fine-crystalline fluorides of rare earths and oxy-halogenids of rare earth elements (FR patent No 2554122, published 3 May 1985), the size of the crystalline particles reaches some 5 to10 microns, that is, basically, not applicable in most printing techniques. Besides, luminophor based on oxy-halogenids of rare earths, change their characteristics with time passing. At that, the marking executed by such composition, is easily visualized by means of generally known methods, which feature reduces efficiency of the passive protection of the documents against forgery.
Also known is the luminescent composition for marking securities, containing fine-crystalline gadolinium oxifuldid activated by terbium, and yttrium oxifuldid activated by ytterbium and erbium, taken in the ratio of some 2:1 to 1:2 (RU patent No) 2253665, published 0.06.2005). The size of crystalline particles of the said luminophors does not exceed 1.5 microns. The prepared composition is added to a printing ink and is used for covering a surface to be marked, by usual printing technique, in the form of a label invisible at usual illumination. The label is visualized when illuminated by a light source emitting infra-red and/or ultraviolet radiation which provokes its light emission in green color. Then, the identification of the document takes place and the conclusion about its authenticity or falsification is made.
It should be noted, that all above compositions for marking securities and important documents include, at least, two components are provide for one or two levels of protection.
At that, the most essential drawback of the luminophors based on inorganic REE compounds consists in their low, in comparison with organic REE complexes, intensity of light emission.
The most similar solution-analogue to the claimed compound, by chemical composition and structure, and also by application, is the compound belonging to the class of REE mixed ligand complexes di-(nitrat-acetyl-acetonate)-1,10-phenanthroline lanthanide (III) 1,10-phenanthroline, where lanthanide—Tb or Dy.
The said compounds can be used as thermo-luminophors for detectors and ionizing radiation dosimeters (the USSR inventor's certificate No 1679769, published 27 Mar. 1996).
At the same time, in case of their use for marking valuables, these known compounds can offer only two levels of protection, at that, they have inadequate intensity of thermo-luminescence.